The subject matter disclosed herein relates to turbine systems, and more particularly to a cross-fire tube purging arrangement, as well as a method of purging a cross-fire tube.
Adjacent combustors of a gas turbine engine are typically connected by cross fire tubes to ensure substantially simultaneous ignition and equalized pressure in all combustor chambers of the gas turbine engine. It is common for less than all of the combustor chambers to include an ignition component to initiate a flame. In such an arrangement, the cross-fire tube allows a flame to pass from one combustor chamber to an adjacent combustor chamber. The cross-fire tubes may also be required to pass the flame from lighted to unlighted premixing regions of the combustor chambers during a light-off operating condition between a premix operating condition and a steady state operating condition. In the premix condition, the region of the combustor chamber connected by cross-fire tubes has no flame and is used for premixing the fuel and air, while in the light-off operating condition this same region has a flame.
When the cross-fire tubes are not in use, they must resist the unwanted passage of either hot gases from combustion or unburned fuel in the premixing zone from adjoining combustor chambers, which may lead to melting of the cross-fire tube or re-ignition of the premix zone of combustion. Resistance may be imposed by introducing a purge air to the cross-fire tube, however, constant purging is not desirable during all operating conditions, such as during ignition that leads to the light-off condition which requires passage of the flame from one combustor chamber to another.